The present invention relates to back supports, and more particularly, to a support which is of selectively variable degrees of hardness.
There have been provided in the prior art a number of disclosures of back supports, and of mattresses, and the like, some of which are directed to the problem of varying the resiliency or hardness or softness of the back support or mattress.
Stone U.S. Pat. No. 2,874,390 describes a mattress and cushion construction which includes interior coil springs which support a padding that is to be engaged by the body of a person. The coil springs are supported on groups of parallel upper rods, and below these upper rods are lower rods, against which rests another set of coil springs which engage padding on the opposite face. A mechanism is provided for moving the upper and lower rods towards or away from each other, the mechanism comprising a rod having left and right hand threads, nuts mounted on the threads, a first pair of arms extending from the nuts to one of the rods, and a second pair of arms extending from the nuts to the other rod. The movement of the rods towards or away from each other is stated to have the effect of varying the resiliency of the mattress, to taste. This patent also discloses that instead of coil springs, foam rubber or similar resilient material may be employed, and in such case a flat surface such as a board may be used to bear against and compress the resilient material uniformly throughout the mattress, and that in such an arrangement, the noted upper and lower rods would bear against and move these flat surfaces. The foregoing disclosure is one which requires boards to be mounted on and extend along a resilient pad, and to compress the pad generally perpendicularly to the face thereof upon which the person rests. Further, the only suggestion provided is of a construction in which the compression of the pad will be uniform.
Also known is Giese U.S. Pat. No. 3,095,188, which is directed to a back rest which will effectively support the lower part of the spine, and which can be adjusted to individual requirements, the back rest being used in a motor vehicle. There is disclosed a layer of foam rubber, having a covering, with a spring supporting it, and of generally part-elliptical shape, having a pair of spaced, free ends which are connected to movable elements to bring the free ends closer together, or permit them to move further apart. Such movement will vary the configuration of the spring, causing it to arch more or less, and thereby change the resiliency of the back rest. In this construction, there is no variation in the resiliency of the foam rubber pad, but only of the noted spring.
Sherman U.S. Pat. No. 3,608,960 is directed to a seat back, and generally provides an adjustable cushion contour, in order that the seat back may be comfortable to people of various anatomical shapes.
Schuster U.S. Pat. No. 3,490,084 and Schuster U.S. Pat. No. 3,851,430 disclose cushions having a foam rubber or plastic layer which is resilient and has a wire or rod extending through it, on which are threaded a plurality of bead-like elements. By providing more or less tension to the ends of the wire or rod, more or less resistance to curving or arching of the wire or rod under load is provided, and accordingly this construction provides variable support for the foam plastic or rubber cushion.